My 15 Year Old Daughter Broke Out With An Itchy

My 15 year old daughter broke out with an itchy rash on her face yesterday afternoon. It has spread to her entire face. I have tried to give her Benadryl both orally and topically and it has only gotten worse. she developed a severe headache earlier today after lunch and that has proceeded to get worse as the day has progressed. Nothing is helping. Water and food isn't helping.